Centralized traffic controlling system for railroads



Oct.21, 1941. WDHMLES HAL 2,259,561

CENTRALIZED TRFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 22, 1938 Q 14 Sheets-Sheet l INVENTORS THEIR ATTOINEY Oct. 21, 1941. w. D. HA!LES ETAL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 14 Sheets-Shet 2 Filed March 22, 1958 mvsmons VgPHaHes and FWBrixner' WM @fid THEIR ATTORNEY 3 gm d vmpuuzzo :QQBNGS 5 125 15 mcod 23m m wnw Oct. 21, 1941. w. 13, HAILES ETAL I 2,259,561

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CENTRALIZED TRAFFIC CONTROLLING SYSTEM RAILROADS Filed March 22, 1938 14 Sheets-Sheet 4 INVENTORS WDWZZ EWBHxner BY M Y THEIR ATTORNEY Oct. 21, 1941. w. D. HAILES ETAL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 22, 1938 14Sheets-Sheet 5 1 1* Q g g A? J N n Y.

II po m N Q- J; g B m n A ii a '8; 0 n INVENTORS WDHailesand FWBriXner THEIR ATTOR;NEY

1 0111.21, 1941. w. b. HAILES Em 1 2,259,561

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 22, 1958 14 Sheets-Sheet 7 I Connected at FIG. 13 v End Statiafl\ 1 7 1o 1 T5 411 i 41 Q 5 1 4 1 161 I g 1 SM '',155 162:! |19 179 [J '17 a 4 H II 255 25h! 5 188 431 INVENTORS g1). HQJ [es and FWBrI'Xner TH EU? ATTORNEY Oct. 21, 1941. w. D. HAILES ETAL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 14 sheets-sheets Filed March 22, 1938 En ixiv E :L Y 5 E R an m a 0 W? H mm A Oct. 21, 1941. w. D. HAILES ETAL CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Marh 22, 1938 1 4 Sheets-Sheet 10 Gem mmMI

, INVENTORS W.D.Hai Ies and FWBrixner ownqt mwm w THEN? ATTORNEY Oct. 21, 1941. w. D; HAILES ET AL 2,259,561

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 22, 1958 14 Sheets-Sheet 11 i FIG-.IQA. v i .1 CONTROL CYCLE SEQUENCE CHART i Direction of Arrows Indicates the Position to which the Delays are Operated A Length of Arrows Indicates Approximate Deia'tive timing of Relay Operations Necessary To Provide a Proper Sequence of Operation Star't Field Station Field Station No.1. No.2.

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CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed March 22, 1938 14 Sheets-Sheet l3 FIG-ALA.

INDICATION CYCLE 5EQUENc-E CHART Direction of Arrows Indicates the Position to which the Relays Are Operated Length oFAr'rows Indicates Approximate Relative Timing of Relays Operations Ne'ceesaig 'to Provide a .'Proper Sequence of Operation;

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INVENTORS 4 VgelHarles and EWBrixner THEIR Anoniqsy J Patented Oct. 21, 1941 CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS William D; Hailes, Brighton, and- Frederick W. Brixner, Gates, N. Y., assignors to General Railway Signal Company, Rochester, N. Y.

Application March 22, 1938, SerialNo; 197-,404

26 Claims. (01. 177-353) This invention relates to centralized traflic controlling systems for railroads, and it more particularly pertains tosuch systems of the coded two-wire simplex communication type.

In a coded centralized traffic controlling'system for railroads, track switches and signals distributed throughout the territory included in the system are controlled from a control ofiice overa code type communication system. Those track switches and signals relatively close to each. other, together with the apparatus for governing their operation, constitute a field station of. such system. The manual control of the track switches and signals for the several stations is accomplished by the transmissionof electrical impulses, forming codes, from the control office to .each of those stations, one at a time, over a line circuit which extends from the control-office through the several stations to the most distant field station. Such manual control of the system is supplemented by the usual automatic block signal system and other local means ordinarily provided to guard against unsafe train m-ovements and improper operation of track switchesand signals.

This invention provides a coded centralized trailic controlling system by which controls and indications are transmitted over'a two-wire main line circuit extending between the control office and the field stations in such a manner, as to include in series. a line relay at each main line field station. and at the control office. A two-wire repeater line .circuit is also provided, together with apparatus which constitutes a repeater station for tying it into the main line circuit. Such control oifice battery supplies energy tothe main line circuit, and a repeater station battery supplies energy to the repeater line circuit. The'line circuit is opened and clos'edat that field station to effect. its'en'ergizationwith a predetermined number of impulses separated by time spaces, both of a selected length. Each impulse operates step-by-step mechanisms at the control oifice and at the transmitting field station in synchronism through. a cycle of operation, irrespective of the length of the impulses and time spaces. The first part of such a series of impulses constitutes a stationregistration code, and the second part of such a series of impulses constitutes an indication code to be registered at the control oflice. l

The system is of the simplex type, that is, the transmission of controls and indications is effected only on differentcycles of operation. It is to be undlerstobd'however, that the scope ofvarious novel features of" the present invention is ,a repeater line circuit includes in series a line relay at each repeater line field station and at the repeater station. The repeater line circuit provides. that the system can include a greater territory than would be practical to include in one single line circuit. 7 c

For the transmission of controls from the control office to any one of the field stations, a predetermined number of impulses of selected polarity are applied to the line circuit, each impulse operating step-by-step mechanisms at the control office and at the field stations in synchronism through a cycle of operation. The first part of such a series of impulses constituting a station selecting code, andthe second part of such a series of impulses constitutes a control code for the particular station selected to receive the controls. c

For the transmission of indications from any one of the field stations to the control oflice, a

not: limited to systems of the simplex type.

The line circuit is normally maintained energized: when the transmitting means at the control oifice and at the field stations isinactive. Such energization is of a negative polarity; The periodof time during which both transmitting means are inactive is conveniently called a period of rest.

& field station can be initiated into a cycle of operation for the transmission of indications only if the line circuit is first energized with negative polarity during a period of rest. Thus the negative energization of the line circuit during a period of rest provides a permission for a start from the field stations. As a means for registering a field start at the control oflice, the field station having indications to transmit, momentarily opens the line circuit.

The control of the polarity of energization of the'line circuit is maintained at all times at the control oflice. Thus, the control office determines whether or not a permission polarity is to be applied to the line'ci'rcuit at the end of each cycle of operation. If there are controls to be transmitted at the end of a cycle of operation, positive polarity is applied to the line circuit. If there are no controls tobe transmitted at the end of a cycle of operation, the permission negative polarity is applied to the line circuit.

There is a conditioning period at the beginning of each cycle of operation for so conditioning the system that the transmitter can maintain control of the line circuit throughout the cycle. Such conditioning takes place during a, period of all field stations is suppressed because of lack of permission polarity. If the. control ofiicev and a field station start a cycle of' operation simultaneously, the control office gains control .of'the.

system for the transmission of controls by applying positive energization to the line circuit to rule out the field station start and condition the system for the transmission of controls.

' After the conditioning has been completed, the line circuit is impulsed by the transmitter. The periods of deenergization during such impulsing are conveniently called offv periods, and. the periods of energization are conveniently called fon periods.

During the transmission of indications, the length of the long on and off periods is determined by the time. required for the dropping A still further object of this invention is to extend the territory that can be efiiciently lncluded in such a system by the use of repeater stations.

Other objects, purposes, and characteristic features of the present invention will be in part obvious from the accompanying drawings and in part pointed out as the description of the invention progresses.

' 1 In describing the invention in detail, reference will be made to the accompanying drawings, in which those parts having similar features and functions are designated throughout the several figures by like letter reference characters which are generally made distinctive either by reason of preceding numerals representative of their location or by reason of succeeding numerals representative of the order of their operation, and in l which:

away of slow release timing relays which are selectively controlled in accordance with indications to be transmitted. At the control office, long on and off periods are detected by detector relays which are maintained energized so long as the periods for which they are provided are short, but which are dropped away whenever the periods for which they are provided are long. In accordance with this invention, means is provided whereby the transmission of indications is so distributed between stations that each of a group of stations having indications to transmitat the beginning of a series of cycles can transmit only one cycle of operation until the system has passed through a prolonged period' of rest. Changes occurring at field stations during a series of cycles are effective for starting. the transmission of indication cycles only after the system has passed through a prolonged period of rest. If there are a group of stations at a particular field location, each of those. stations has an opportunity to transmit one and. only one indication cycle during a series, whenever that particular field location gains control of the line circuit.

An object of this invention is to provide an eflficient two-wire simplex communication syss tem, using a control ofiice battery as a source of energization for the line circuit for the transmission of both controls and indications, whereby the control office transmitter gains and maintains control of the line circuit by the selection of the polarity of its energization, even in case of a' simultaneous start between the control o flice transmitter and a field station transmitter.

Another object of this invention is to provide a means dependent upon the operation of comparatively quick acting relays having comparatively constant characteristics for detecting the difference between long and short, off and on periods.

A further object is to so distribute the facilities of the system for the transmission of indications among the field stations, that each station transmits its indications with a minimum delay aftera change has occurred in the position of any of the devices at that station.

Figs. 1A and 13, when placed end to end, illustrate in a simplified manner certain of the features provided by this invention relative to the line circuit extending between the control office and the field stations;

Figs. 2, 3 and 4 illustrate the apparatus and circuit arrangement employed at the control office, Fig. 2 being relative to the selection of the polarity to be applied to the line circuit, Fig; 3 being relative to the stepping and to the reception of indications from the ,field stations, and Fig. 4 being relative to the registration of indications received from the field stations;

Figs. 5A and 5B, when placed side by side, illustrate the apparatus employed at a typical field station arranged and controlled in accordance with the present invention; v

Fig. 6 illustrates a means provided by this invention, also shown in Figs. 5A and 5B, for distributing indication cycles among all stations having indications to transmit at the beginning of a series of successive cycles;

Fig. 7 illustrates a means provided by this invention for distributing indication cycles among all stations having indications to transmit dur ing a series of successive cycles. Fig. 8 illustrates how the distribution of indication cycles is accomplished where a plurality of stations are provided at a particular field location;

Fig. 9' illustrates a means provided by this invention for repeating control and indication impulses into a branch line circuit. For convenience in considering the application of the repeater station the drawings have been provided in such a manner that Fig. 9, when placed between Figs. 3 and 5A illustrates how the repeater s'tation may be placed between the control ofiice and the field station illustrated in detail, and Fig. 9, when placed at the side of Fig. 5B, illustrates how the repeater station can be connected between any particular field stations.

Figs. 10A and 10B, when placed one above the other, constitute a chart illustrating the sequence of operation of the relays during a specific control cycle.

Figs 11A and 113, when placed one above the other, constitute a chart illustrating the sequence of operation of the relays during a specific indication cycle.

In order to simplify this disclosure, reference is made from time to time to functions common to all parts of a similar character by use of the letter reference characters without preceding or succeeding numerals. It is to be understood that such a reference applies to any parts designated in the drawings by reference characters which aresimilar except for numerals associated therewith. V

For the purpose of simplifying the illustration and facilitating in the explanation, the various parts and circuits constituting the embodiment of the invention have been shown diagram-matically and certain conventional illustrations have been employed, the drawings having been made more with the purpose of facilitating the disclosure as to the principles and mode of operation, than with the idea of illustrating the specific construction and arrangement of parts that would be employed in practice. Thus the various relays and their contacts are illustrated in a conventional manner, and symbols are used to indicate connections to the terminals of batteries, or other sources of electric current instead of showing all of the wiring connections to those termimile.

The symbols and are employed to indicate the positive and negative terminals respectively of suitable batteries or other source of direct current; and the circuits with which these symbols are used always have current flowing in the same direction. The symbols (B+) and (B-) indicate connections to the opposite terminals of a suitable battery or other direct current source which has a central or intermediate tap designated (CN); and the circuits with which these symbols are used may have current flowing in one direction or the other depending upon the particular terminal used in combination with the intermediate tap (CN). When'altern'ating current is used in place of direct current, the particular symbols employed represent the relative instantaneous polarities.

Apparatus Control ofiice equipment.-The control oflice equipment (see Figs. 2, 3 and 4) includes a control machine having a group of control levels for each'field station, a miniature track layout corresponding to the actual track layout in the field, and various indicator lamps or equivalent devices together with apparatus and circuits to accomplish the desired operation of the system.

Thepart of the control ofli'ce illustrated: shows more particularly that portion of the control ma.- chine which is typical of the apparatus associated with a single field station having a track switch, a crossover or the like, together with the general transmitting apparatus employed in common by all of the field station units provided for the system.

In accordance with the present invention various functions can be controlled from the control machine, but for the purpose of simplifying the present disclosure only a switch machine control lever SML together with self-restoring start and cancel buttons B and CNB respectively have been shown, it being understood that the control of the track switch from the control machine by the operation of lever SML is typical of the means which is provided for controlling other devices at the various field stations.

Associated with each group of control levers is a change storing relay CH and a code determining relay CD. The actuation of a start button B causes the energization of its corresponding change relay CH, which in turn energizes its associated code determining relay CD, provided the system is at rest. If the system is in operation the relay CH remains energized to cause the initiation of a control cycle and the picking up of its associated relay CD when the system reaches a period of rest.

Inthe event that several starting buttons are actuated simultaneously or in rapid succession, the change relays CH and code determining relays CD together with a code determining stick relay CDS, are so interlocked that only one code determining relay may be picked up for any one particular cycle of operation, and that interlock is so arranged that the relays CD are picked up in a predetermined sequence, depending upon their position in the circuits.

Associated with the contacts of each code determining relay CD (see Figs. 2 and 3) are code jumpers which selectively connect the circuits associated with the contacts on that relay to the relays PC and NC which are provided for applying energy to the line circuit from a line battery CE. The relay PC, when energized, causes the application of positive energy to control line wire it)? of the line circuit, and the relay NC, when energized, causes the application of negative energy to that line wire.

In response to the energization of the line circuit, a quick acting neutral relay F is picked up, and its energization during av cycle of operation causes the energization of the quick acting repeater relay FA.

In order to eifect the proper timing of certain of the relays employed at the control office, and in order to provide other features relative to. the operation of the system, the relays SA, SB, SC

and SD are provided. Relay SA has such slow acting characteristics as to remain in a picked up position between the energized impulses of the line circuit. Should the time between the impulses of the line circuit be of a length of time longer than that required for the transmission of control and indication codes, the relay SA drops away and terminates the cycle of operation.

The slow acting relay 0C serves to restore the system to normal. in the event that an energized impulse longer than that required for the transmission of control and indication cycles is impressed upon the line circuit during the transmission of a series of impulses.

A bank of stepping relays has been shown as having the relays VI, V2, V3, V4, a last stepping relay LV, and a half-step relay VP. The number of steps being determined by the number of stations to be connected to the line circuit and the number of different devices to be controlled and indicated.

An impulsing relay E is jointly controlled by the stepping relays and the half-step relay VP, and its functions are to apply and remove impulses to and fromthe line circuit during a control cycle and, together with its associated repeater relay EP, to start the long time intervals that are detected by relays TON and TOP during long on and off periods of an indicated cycle.

Relay TON remains energized during an indication cycle if the line impulses are of comparatively short length, and drops away during each long impulse.

Relay TOF' remains energized during an indication cycle if the time spaces between the line impulses are comparatively short, and drops away during each long time space between impulses.

The relays LON and LOl respond, during an indication cycle, to the dropping away of relays 'I'ON and TOF respectively, and the positioning of relays LON and LOF determinesthe position station registration, the relays PON and POF are:

positioned on the first and second steps of the indication cycle in accordance with the positions of the message receiving relays LON and LOF respectively. If a larger number of field stations is employed than can be registered by this bank of pilot relays, more steps may be employed and additional pilot relays may be provided. Following the positioning of the pilot'relays, a registration execution relay RX is picked up to provide energy for a station relay ST which is selected. in accordance with the station to be registered. Although a station relay ST is provided for each field station and is selected in accordance with that station registering code, only one ST relay has been shown, thus the operation of that relay is to be considered as typical of the operation provided for the relays ST provided for each of the other field stations which may be included in the system.

Following the registration of a station by the picking up of a station relay, suitable indication storing relays, such as relays RON and ROF, for

example, which are of the two-position polarized magnetic stick type, are positioned on the remaining steps of the indication cycle for storing the indications received from the field station which has been registered.

'Relay OR (see Fig; 2) is an auxiliary relay which is normally energized and is dropped away at the beginning of each cycle and again picked up in the period of rest. Relay OR provides the line circuit with a low degree of energization during periods of rest and also provides means whereby a series of indication cycles can be interrupted for the transmission of a control cycle.

Relay C (see Fig. 2) is provided for the purpose of starting the system into operation to transmit a control cycle, and relay CF is for the purpose of starting the system into a cycle of operations in response to a start from a field station.

Various resistors R. are provided at the control office 'for providing various features relative to the control of the relays and relative to the drainage of the line circuit. I

The control ofiice equipment also includes various sources of current supply, bus wires and circuit connections, indicator lamps, over-load protection and such other devices as may be needed for the proper functioning of such a system.

Field station equipment-The field station 'ap' paratus illustrated in Figs. 5A and 5B of the accompanying drawings is typical of all field stations of the system and may be adapted for use at the first, second, or any other. location included in the main line circuit, or may be adapted for use at any stations included in the repeater line circuit beyond the repeater station illustrated in Fig. 9. The only necessary change from the typical field station shown is in the position of the two groups of code jumpers, which are arranged differently at each location in order to provide for the selection of that particular station at times when control codes aretransmitted, and for the registration of a station at the control oflice at the beginning of the transmission of an indication code. For convenience in the description, it has been assumed that the field station illustrated is the first field station along the line circuit extending from the control office, and is so designated by reason of the preceding numeral I employed.

With reference to Fig. SE, a turnout track is;

illustrated as connected to a main track by a track switch TS which is operated from one extremelocked position to the other by a suitable switch machine'SM.

The switch machine SM is governed by a switch machine control relay SMR which is of the twoposition polar magnetic stick type and which is governed from the control ofiice by means of the communicating system provided by this invention. The relay SMR controls the operation of the switch machine SM by energizing its normal or reverse operating wires in any suitable well known manner so as to provide proper protection for the safe operation of the track switch TS;

Suitable signals are associated with the track switch TS for governing traffic thereover and are provided with automatic block signalling means with selections made in accordance with the posi-' tion of the track switch TS and the condition of the detector track section. In addition to the automatic means for governing the signals asso-- ciated with the track layout, the signals are also controlled from the control office by means of the communicating system provided by this invention in a similar manner to that illustrated for the control of the track switch TS, various modifications being employed to meet the requirements of practice.

Associated with the signals governing traflic over the track switch TS is a suitable normally energized indicating relay M which is deenergized whenever a signal is cleared for governing traffic over that track switch.

A detector track circuit having a track relay T. is provided in the usual manner for the track section including the track switch TS.

The communication part of the system at the field station includes a three-position biased-toneutral polar line relay IF together with its quick acting repeating relay IFA. Slow acting relays ISA and ISB correspond to similar relays provided at the control office in that they are picked up in the conditioning period at the start of a cycle of operation, and are held up throughout that cycle.

As a means responsive to the transmission of a station selecting code from the control ofiice during a control cycle, the relays ISO and ISOS' are provided and are controlled in such a manner that relay ISO remains energized during a control cycle only so long as the code impressed upon the line circuit corresponds with the code assigned to that field station. The energizing circuit for the relays SO and SOS includes code jumpers which, by their positions, determine the particular code required to select that station.

The field station includes a bank of stepping relays comprising half-step relay IVP and stepping relays VI, V2, V3, V4 and LV. These relays'are operated in synchronism with the similar stepping bank provided for the control office, with the exception that the stepping'relaybank at the field station is dependent upon station selection during the transmission of either control or indication cycles.

A change relay ICH and its repeater relay ICI-IP is provided to register a change in the position of certain of the traffic controlling devices at the field station in order to initiate the transmission of an indication cycle.

A lockout relay L0 is provided for each field station for the purpose of making effective the transmission of indications from but one of several stations having indications to transmit.

when a station has new indications to transmit, the .relay LO .for that station is energized momentarily, during a period of rest, and the moment'ary picking up of that relay opens the line .circuit to register, in the control ofiice, the start of. an indication cycle. Relay LO picks up again at the end of the conditioning period and it remains pickedup during the stepping only at the location that is permitted to transmit indications. When relay L is in the picked up position it terminates the line thus disconnecting the more distant portion of the line and thereby rulingout all more distant locations. Auxiliary line lockout means is provided by the combined operation of relays RL and Let the beginning of a cycle of operation for purposes pointed out hereinafter.

Relay S is provided in order to supply an additional circuit to support the SA relay and prevent the SA relay from releasing during long ?off time spaces occurring during an indication cycle. The S relay also provides the means for preventing the release of the indication storing repeater relay CHP during a control cycle.

Relays E at the field stations perform a function similar to relay E in the control office in that they effect the impulsing of the line circuit, such impulsing being rendered effective only for the transmission of indications from the field stations to the control ofiice.

, Relays LON and LOF at the field stations govern the length of the impulses and the time spaces between the impulses respectively during the transmission of indications from the field station. The energization of the relays LON and f LOF is dependent upon code jumpers for selecting the station registration code for the indication cycle, and on thepositions of the relays or devices, of which the positions :are to be indicated, such as relays T and M. Relay LON when energized from such means during an off period provides'that the next impulse should be long, and in a similar manner when relay LOF is energized during an on period it provides that-thenext off period shall be long.

A relay 0C is provided for each field station and is controlled in a similar manner tothe relay OC provided for the control office, with the exception that its control circuits combined with its slow acting characteristics provide that it remains energized throughout a series of cycles-and isreleased at the end of such a series.

With reference to the modification illustrated in Fig; 7, a relay D8 is provided which is picked up only at a field station which is transmitting.

indications,and is maintained in an energized position throughout aseries of indication cycles.

With reference to the modification illustrated in Fig. 8, in addition to the change relays CH and CHP, lockout relays CHL, LC and LCS are provided for causing the distribution of indication cycles in a manner to be hereinafter described in detail.

The field station also includes suitable bus wires, circuit connections, over-load devices, and other devices and apparatus necessary fora centralized trafiic controlling system as contemplated in accordance with the present invention.

Repeater station equipment-The repeater station transmits to the repeater line circuit the control code impulses which are applied to the line circuit at the control oflice, and ;in doing so employs relays 3P0, 3NC and 3G in a similar mannerand for similar purposes as has heretofore been de'scribedfor relays performing similar functions at the control 'ofiice.

Relays 3F, 3P2 and 3FA are responsive to the energi'zation of the line circuits with which they tainingin a picked up position throughout an indication cycle of relay 300, which is controlled in asim-ilar' manner to relay DC of the field station.

Relay registers thebeginning'ofan indication cycle as initiated from a station included in the repeater line circuit, and relay 3LO locks out more distant stations in the main line circuit during the transmission of indication cycles from a station included in the repeater line circuit.

The auxiliary relay 30R is provided for maintaining similar characteristics of the repeater line circuit to the characteristics of the main line circuit as providedby relay OR in the control ofiice.

Relay SE is used in impulsing the'main line circuit during an indication cycle, and the impulsing of that relay is governed by the relay 3E2 which is included in the repeater lin'e circuit.

Various resistors R are provided for purposes which are in part obvious from the accompanying drawings and which will be pointed out more in detail as the description of the invention -pro-- gresses; ,The repeater station also includes suitable circuit connections, over-load devices, and other devices and apparatus necessary fora centralized trafi'ic controlling system as contemplated in accordance with the present invention.

It is to be understood that the relays illustratedhave properv operating characteristics to fulfill the requirements of the system according to the mode of operation herein described and according tothe requirements of practice. It is also to be understood that characteristics of certain ofthe'relays can be adjusted according to the requirements of practice by such means, for example, as the application of shunts across the windings of those relays to effect a greater delay in their dropping away.

It is believed that thenature of the invention, its advantages and characteristic features can best be understood by considering the mode of operation of the system illustrated.

stations whenever there arenew controls or new indications respectively ready to be transmitted.

If new controls for several different field stations are ready for transmission at the same time, they are transmitted on separate cycles, one cycle for each station to be served. If several field stations have indications ready for transmission at the same time they are transmitted from such field stations to the control ofiice, onecycle for eac h'station; The lockout feature is effective to allow only one field station to obtain access to the line circuit during any one cycle.

Normal at rest conditions.When the system is at rest, the line circuit is maintained energized in order that any field station can regis- -ter at the control oflice the need for an indication cycle by a momentary interruption of the line circuit.

The line circuit is energized with negative polarity when the system is at rest to permit any ofithe field stations to initiate an indication cyinafter described in detail. Such energization is maintained by a stick circuit for relay F in the =control'ofiice which includes a limiting resistance R. forthe purpose of conserving energy from the battery CB, it being obvious that once the relays the'line circuit are positioned at the end of a.cyc1e of operation, as will be hereinafter described, less energy is required for maintaining those relays in their last operated position.- .,In orderto simplify the description of the present invention reference is made from time toQtimeto the positive or negative energization of the line circuit, which is to be understood as .meaning the application of positive or negative energy respectively to the side of the line circuit which includes the. relays F and which leaves the control office aswire Ill (see Fig. 3).

During a period of rest, relay NC (see Fig. 2) is .maintained in a picked up position by a stick ,circuit which, similar to the line circuit, includes .a limiting resistance R2 for conserving energy and also for making relay NC quick in dropping .away. ,The stick circuit for maintaining relay NC in" apicked up position during a period of rest is closed from through a circuit including back contact II of relay SD, back contact I 2 ofrelay C, back contact I3 of relay CF, front contact I4 of relay F, resistance R2, front contact Iiiv of relay NC, and winding of relay NC, to

;, The line circuit is normally energized (see Fig.

.3), from the negative terminal of battery CB, through a. circuit including back contact-I6 of relay PC, front contact I! of relay NC, winding of, relay IF (see Fig. A), back contact I46 of .relay ILO, the winding of the relay F and the back contact of the relay LO for each of the other stations, return line wire I8,.front'contact I9 of relay NC, back contact of relay PC,

winding of relay F, front contact 2I of relay F,

.and resistance R, to the positive terminal of battery CB.

Relay OR (see Fig. 2) is normally energized in order to open the pick up circuitsfor relays NC and F during a period of rest. A circuit is closed for energizing relay OR during such a period,

from ,througha circuit including back contact 22 of relay C, back contact 23 of relay CF, front contact 24-of relay F, and winding of relay A stick circuit is also closed for relay OR from through a circuit including back contact 28 of relay SA, front contact 29 of 'relay OR, and winding of relay OR, to

The stick circuit maintains relay OR picked up at the beginning of a cycle for reasons hereinafter pointed out.

At the'fielcl station illustrated (see Figs. 5A

and'5B), relays T, M, ICH, IF and IRL are norl ,70 :fice, the momentary depression of the start but- .mally energized. Relay T is of course energized from the usual track circuit battery and, although its position has been shown as that assumed when the track circuit is unoccupied, it

is to be understood that the system can as .well be in a period of rest when the track circuit is occupied so as to cause the deenergization of relay T, such period of rest being reached after the indication has been transmitted of the change in the position of the relay T. A similar mode of operation is effected relative to the positionof .relay M for repeating the stop positionof the signals associated with the track layout, that is,

.relay'M can be in either a picked up or a dropped away position during a period of rest. I

Relay ICH is maintained in its energized position during a period of rest by a circuit closed from through a circuit including front con- .tact 25 of relay M, front contact 26 of relay T,

front contact 21 of relay ICH, and lower winding of relay ICH, to It is of course obvious that relay ICH is maintained in an energized position during a period of rest when relays T and M are in either an energized or a deenergized position and is dropped away upon a change in the position of either of those relays.

Relay IRL (see Figs. 5A and 5B) is energized, when the line circuit is energized with negative polarity during a period of rest so as to cause the polar contacts of relay IF to be in a left hand position, by a circuit .closed from through a circuit including back contact 29 of relay I SB,

polar contact 30 of relay IF in a left hand position, wire I4'I, back contact 429 of relay LV, back contact 31 of relay V4, back contact 32 of relay V3, back contact 33 of relay V2, back contact 34 of relay VI, wire I48, back contact 35 of relay IL, and winding of relay IRL, to A stick circuit is closed for relay IRL from through ,a circuit including back contact 36 of relay ISB, winding of relay IL, front contact 31 of relay IRL, and winding of relay IRL, to but such stick circuit is ineffective for the picking up of relay IL as long as the pick up circuit for relay IRL remains closed to shunt out that stick circuit. Relay IL becomes energized, however, as

soon as the pick up circuit for relay IRL is opened as will be hereinafter pointed out.

Manual start.The system can be manually initiated into a cycle for the transmission of'control impulses by. the. positioning of the control levers for therparticular station with which the operator desires to communicate and by followingsuch operation by the' momentary actuation of the start button B associated with those levers.

The arrangement of the circuits-for the control of relays CH, CD and CDS is such as to pro- .vide that only the manual start for one station circuits involved.

After the operator has positioned all of the levers for a particular station, such, for example, as for the station shown nearest the control ofton BI associated therewith (see Fig. 2) closes a circuit for the energization of relay CHI from through a circuit including contact 38 of button BI in a depressed position, winding of relay CHI and contact 39 of button CNB in a 

